This invention is related to the power generation industry and, more particularly, to the field of monitoring conditions of electrical generator systems.
In the power generation industry, monitoring the conditions of components of electrical generator systems can be critical to the efficient and nonhazardous functioning of such systems. Effective monitoring encompasses detecting and registering conditions in various components including generators, exciters, collectors and large utility transformers. Conventional techniques for monitoring the temperature of such components use thermocouples or resistance temperature detector devices which convey temperature information with conductors. Such devices and techniques, however, are limited and suffer from several deficiencies. For example, these devices cannot be routed across components operating at high voltage or where there is the risk of flash-over and emf distortion. The ability to measure accurately the temperature of a component is thus further limited because temperature measuring devices cannot be positioned in proximity to critical areas whose temperatures it is desirable to monitor. Therefore, critical areas cannot be monitored well using these conventional devices and methods.
These limitations on condition monitoring, moreover, often necessitate monitoring by visual means, which, in turn, can require that visual inspections be scheduled at periodic intervals with any attendant costs associated with the downtime of the electrical generator system that may be necessitated while such inspections are performed. Moreover, because such visual monitoring can only be undertaken at intermittent intervals, there is no capability for substantially continuous monitoring of electrical system components. Thus, such conventional techniques and devices suffer deficiencies in terms of both efficiency and efficacy in the sense that they are costly if there is necessary downtime of the system and are inevitably less reliable when they can only be effected on a limited basis rather than continuously.
Other devices and methods have been tried for certain types of components, but these also suffer from other limitations and deficiencies. For example, U.S. Pat. No. 4,818,975 by Jenkins titled xe2x80x9cGenerator Stator Core Temperature Monitorxe2x80x9d proposes measuring ambient temperature of the stator core of a generator in terms of hydrogen gas (H2) exiting through the stator core. Temperature of the core can be inferred from either of two effects: (1) the hotter the gas, the more frequent the gas molecules impinge on a temperature-responsive liquid crystal so as to block monitored light; and (2) the hotter the gas, the greater the expansion of a housing-mounted flexible bladder thereby influencing the angle and hence amount of light detected. There are at least two serious limitations with this type of monitoring, however. First, owing to the relative diffusion of gas molecules, gas is a less efficient heat conductor. Accordingly, the hydrogen gas is a less efficient, less reliable conveyor of temperature information. Second, and more fundamentally, this type of monitoring measures only an aggregate or average temperature of the environment surrounding the stator, not the actual temperature of a specific system component. This can be especially limiting given the obvious need to detect and isolate a temperature variation occurring in individual components. Measuring ambient temperature does not permit separable monitoring and detecting temperature variation in individual components. Detection, moreover, is obviously delayed until, for example, an overheating condition in a single component contributes sufficient heat to raise the average or ambient temperature surrounding the stator or other electrical system.
U.S. Pat. No. 4,203,326, by Gottlieb et al. titled xe2x80x9cMethod and Means for Improved Optical Temperature Sensorxe2x80x9d proposes an xe2x80x9coptical conductorxe2x80x9d to measure temperature, but does not address directly the problems of the more conventional type conductor temperature information conveyors. Such devices combine an optical core with cladding along with a jacket to encase the core and clad material. The core and clad material are formed so as to produce a temperature-influenced difference in refractive indexes that is intended to overcome a common problem with such conductors: temperature responsiveness varies linearly with the length of the conductor. But whatever deficiencies may be corrected with respect to this conductor-length factor, such a device registers only a temperature range and does not address other problems described above. Moreover, there are additional limitations inherent in such devices that limit the efficiency with which temperature detection can be performed. First, thermal disruption of the fiber conductor by melting in the fiber or surrounding cladding disturbs light conduction. Although using different cladding material can compensate for this risk, doing so can further complicate choosing a proper material composition that will provide the correct refractive indexes difference to accurately monitor for temperature variation. Finally, in addition to their above-described complications in achieving a desired result, such devices also are fundamentally limited in the result that is achieved. Specifically, such devices provide detection of only a range of temperatures, thereby providing less-than-desirable accuracy and problematic delay in monitoring for critical conditions like overheating in an electrical system component.
There is thus a critical need for an apparatus or method that overcomes the problems inherent in conventional and optical conductor type devices for monitoring electrical generator components. Specifically, there is the need for a device or method that more accurately, more efficiently, and more simply detects and isolates temperature variations in the components of electrical generator systems.
In view of the foregoing background, the present invention advantageously provides an apparatus and method for efficiently and efficaciously monitoring the temperature of electrical generator system components in the presence of such inhibiting factors as high voltage and flash-over risk. The present invention provides a more accurate capability for monitoring temperature and detecting temperature variation in electrical system components. Moreover, although the apparatus and method are described herein in the context of electrical generator systems, they have wide applicability in other contexts as will be apparent to one skilled in the relevant art. Such uses include monitoring air conditioning systems and other building service devices whose temperatures need to be monitored effectively and efficiently on a substantially continuous basis. Specifically, as described herein, vital temperature information using the apparatus and method of the present invention is directed efficiently and rapidly to a temperature variation monitor so as to monitor critical temperature variations in a direct, efficient, and reliable manner.
Further advantage is provided in that critical temperature information can be conveyed from within the system to a remote site. This provides capabilities for safe, continuous temperature monitoring using the apparatus and method of the present invention. Notwithstanding this significant advantage, the present invention can be used just as effectively for direct local monitoring of a system component""s temperature.
The present invention, moreover, specifically provides the capability of strategically positioning a plurality of temperature monitoring devices or xe2x80x9cprobesxe2x80x9d at any number of selected critical areas within an electrical generator system. This provides capabilities for monitoring and detecting temperature variations of a plurality of discrete components within the system as opposed to only measuring an average temperature in the form of ambient temperature of the overall system. Again, the present invention permits multiple component monitoring from a remote location external to the electrical generator system as well as direct, on-site temperature monitoring.
The apparatus and method of the present invention provide an effective, efficient temperature probe that preferably includes a light source, a light sensor, a light window, and an associated pair of light guides along with a direct temperature information conveyor in the form of a thermal conductor linking the light window with the electrical system component whose temperature is to be directly monitored. More specifically, the light source and light sensor can be positioned outside of the electrical generator system, while the light window is positioned within the system at any selected critical area. A light guide conveys light from the light source to the light window. The light window is responsive to temperature and receives temperature information directly and virtually instantaneously from a thermal conducting connector in communication with a surface of the component whose temperature is to be monitored. Within a preselected temperature range deemed to be acceptable, for example, the light window remains transparent, but if the temperature falls within a preselected critical range, the window responsively becomes opaque and blocks the light that otherwise would have been captured by the second light guide to be conveyed to the light sensor.
Thus, a specific advantage of the present invention is the ability of the heat conductor to convey accurate and ready temperature information. The conductor is in direct contact with a surface portion of the select component whose temperature is to be monitored. The temperature so measured is that of the specific component rather than an aggregate or average of the system, as taught by existing conventional and optics-based devices.
Whereas other methods and devices detect variation in ambient temperature by registering increased or more rapid average impingement of gas molecules on the surface of a liquid crystal to raise the temperature of the crystal, the present invention uses a heat conductor having high thermal conductivity. More specifically, recognizing that temperature information is transferred more rapidly through a medium having a fixed structural arrangement, the present invention employs a thermal conducting medium that preferably is a metal or other medium having a sufficiently high coefficient of heat conduction. Thus, the translational (or kinetic), rotational, and vibrational energy is transmitted more rapidly and exchanged more efficiently with a temperature-sensitive liquid crystal device. This, then, increases the speed and accuracy with which temperature information can be conveyed, as noted above. Thus the present invention in contrast to other devices and methods allows earlier and more accurate detection of temperature variation in electrical system components.
As also noted above, a further, albeit related, advantage stemming from use of a light window directly connected via a thermal conducting medium to the component, is that the temperature of the component itself is conveyed rather than a proxy in the form of the ambient or system environment temperature. Again, the temperature information conveyed is accordingly more accurate because the heat conductor can preferably be a metal, and moreover, the temperature information is conveyed rapidly as compared to conventional and other optics-based devices.
Yet a further advantage is provided by using the light guides described above, which can enable the routing of the temperature probes across virtually any component without the concerns of high voltage or flash-over that would otherwise arise with conventional devices and methods. In a related vein, the lightweight light guides and light window of the apparatus and method thus ensure a lighter assembly as compared to conventional temperature monitoring devices, providing an additional advantage where weight is a critical factor such as in aerospace and other non-land based applications.
Moreover there is the ability, as also noted above, to do so for a multiple of distinct temperature probes. These features, then, help enable the additional advantage of measuring distinct components within the same electrical generator system. Therefore, because distinct temperature information rather than an aggregate is conveyed for each selected component, the individual components can be simultaneously monitored within the same electrical generator system, whereas with conventional devices and methods there is no capability for distinguishing which of several components is contributing what temperature to the overall system temperature. This feature thus permits discrete, simultaneous monitoring of multiple componentsxe2x80x94generator, exciters, collectors, transformers, etc.xe2x80x94and provides capabilities for singling out with early detection which, among the various components, may be creating a system problem in the form of a temperature variation.